This invention relates to electrical connectors, and in particular, to improvements in or relating to connectors for leadless circuit boards such as leadless integrated circuit packages, leadless large-scaled circuit packages, and leadless printed circuit boards.
In order to removably mount the leadless circuit boards (which will be referred to as "daughter board") employing terminal pads in place of leads onto another circuit board (which will be referred to as "mother board"), connectors have been used in the prior art as disclosed in U.S. Pat. Nos. 3,904,262, 4,063,791, and 4,204,722. Generally speaking, such a connector includes a housing of insulator material for receiving the daughter board therein. A plurality of contact elements are mounted in the housing to engage terminal pads of the received daughter board and to connect with conductor elements of the mother board on which the connector is mounted. Clamping means are used for clamping the daughter board and the connector housing to press the terminal pads of daughter board onto the contact elements.
In conventional connectors of such a type, the clamping means has an upper portion engaging the upper surface of the daughter board and a lower portion engaging a side end or a bottom edge of the connector housing. Therefore, when the daughter board and the connector housing are clamped by the clamping means, an upwardly acting force is applied on the peripheral portion of the connector housing. On the other hand, since each pad is pressed onto a corresponding contact element, a pressure is applied on the contact element. Therefore, another force is applied downwardly through the connector housing and onto the contact element. These upward and downward forces make a moment or a torque because each contact element is generally located apart from the peripheral edge of the connector housing. Therefore, the connector housing is disadvantageously deformed so that the peripheral portion of the connector housing is raised. As a result, the intended contact force cannot be obtained between the pads and the contact elements.